I've done two drop-flat conversions in the past couple weeks. At the co-op, it seems that flat bars sell faster than drop bars for bikes that are "fast & light, but not full-on race bikes". On both, the OEM brifters were gummed up, so that made the decision easier (I eventually plan to completely degum the brifters in the ultrasonic cleaner, but it might be a while). I'll admit I have a pile of flat bar index shifters around here in 7, 8, and 9 speeds, a box of flat bars, and a bin of brake levers for caliper/cantilever brakes, so that helps. On the first one, it seemed relatively straightforward to change out, until I was reminded the hard way that Sora front derailleurs don't like flat bar (MTB pull) front shifters, so I had to swap the front derailleur as well. On the other, the Sora front derailleur spring was broken (a very common occurrence, it seems), so it's reassembling as a 1x9.